Conventional keyboards, having a multiplicity of keys, usually more than fifty in total, are universally used for typing and data entry. These keyboards have a number of significant disadvantages including a long time required for learning their operation, a requirement for continuous practice to maintain proficiency and large size, weight and bulk. Touch typing is required in order to reach speeds of above 150 characters per minute.
The revolutionary development of computer technology has greatly broadened the application of data processing and has brought data input terminals into environments, such as the home and executive offices where they were not previously known. This broadening has made the data input terminals accessible to persons who have neither the time nor the inclination to undergo extended training in the use thereof. In order not to limit tha applicability of data processing to persons who are specially and extensively trained in the use of data input terminals and to extend the availability of data input terminals to environments which greatly limit the permissible size of such terminals, it is necessary to provide data input terminals which can be operated efficiently by persons having a minimum of training and who use the terminals only intermittently. The data input terminals must be sufficiently small to be placed unobtrusively on an executive desktop.
Applicants have identified eight characteristics which are desirable in a keyboard in order for it to meet the requirements of a broad, untrained user population. They are small size and weight, portability, short time required for operator training, convenience of operation, limited operator effort and concentration requirements; short required retaining time after an interruption in use, speed of data entry, and low cost.
Chordic keyboards have been developed in an attempt to fulfill the above criteria. For the purposes of the present specification and claims, a chordic keyboard is defined as a keyboard wherein a plurality of data entry locations must be engaged to produce a single letter or other symbol. Chordic keyboards thus defined may be distinguished from conventional keyboards in which each key defines one or more letters or symbols as well from keyboards in which engagement of a plurality of data entry locations defines a word.
Various types of chordic keyboards are known and are described in the literature. Examples of such keyboards are described in the following publications:
1. N. Rochester, F. Bequaert and E. M. Sharp, "The Chord Keyboard" COMPUTER, December 1978, pp. 57-63;
2. R. C. Sidorsky, "Alpha Dot, A New Approach to Direct Computer Entry of Battlefield Data" Technical Report 249, U.S. Army Research Institute for the Behavioural and Social Sciences, 1974;
3. U.K. Patent Specifications No. 1,496,522 and 1,500,674;
4. U.K. Patent Application No. 2,015,220
The above-described keyboards, while all offering certain advantages in terms of convenience of use do not display any particular advantage in terms of learning time, retraining time or speed of data entry. The chordic keyboards described hereinabove are all characterized in having a relatively large code set which must be learned by the user and mastered in order to provide high speed data entry.
To the best of applicants' knowledge, none of the above-described keyboards has met with commercial success for the following reasons: (1) The large code set makes learning difficult and time consuming and retraining time significant, (2) The code set which associates the letters and symbols with key combinations is not selected for motoric ease, particularly in transitions between letters often occuring together; (3) Symbols and numbers have their own codes which must be learned in addition to the letter codes; (4) Even where a mnemonic link is provided between functions and alphabet letters, the key location combinations are different, even though the finger combinations remain the same; (5) The total number of symbols and control instructions is severely limited particularly in the embodiment disclosed in the aforesaid British Patent Specifications.
Research by the applicants has indicated the importance of key functioning to the overall motoric efficiency of a chordic keyboard. The present invention is directed to keyboard key structures in a chordic keyboard which greatly enhance the operational efficiency thereof.
Generally speaking it is known to use mnemonic devices for teaching code operations. Such mnemonic devices, for example as described in U.K. Patent Specification No. 8,036,839 employ a geometrical association concept in which the shape of a letter or other symbol to be coded has a certain geometrical resemblence to the configuration of engagement locations required to encode or define such a letter or symbol.
None of the prior art literature, including patent literature, on chordic keyboards teaches the use of a group approach to chordic keyboard code teaching.